The present invention relates to improved nonwoven fabrics or webs which are formed by extruding thermoplastic polymer filaments which can be conveyed onto a "forming wire" and bonded to provide structural integrity or extruded as filaments as use in other structures, for example, sliver, staple, and tow.
The use of thermoplastic polymers to form fibers and fabrics as well as a variety of shaped objects is well known. Common thermoplastic polymers for these applications have been polyolefins, particularly polyethylene and polypropylene. Polyolefins as a class tend to be hydrophobic materials and as such are relatively nonwettable by water, making fibers or fabrics made from these materials less than completely suitable for applications which call for wettability. Such applications are as absorbent products like diapers, feminine hygiene products, incontinence products and bandages which generally employ materials which exhibit hydrophilic characteristics. Despite their hydrophobic character, however, polyolefins continue to be the most common thermoplastic fiber forming polymer because of their low cost. As a result, a number of attempts have been made to provide a polyolefin fiber and fabric made therefrom which are hydrophilic and wettable.
In the applications mentioned above as well as others, the product, for example a diaper, may receive multiple liquid insults before disposal. It is important, therefore, that wettability, once imparted to a polyolefin, be durable. A wettable polyolefin in which the property of wettability was substantially reduced or even removed completely after one or even two wettings would probably be of very limited utility for applications with multiple insults. Durable wettability is defined therefore as the ability to become wet after at least three prior wettings.
It is an object of this invention to provide a polyolefin fabric and fiber having durable wettability and which is relatively simple in execution, i.e., requiring no extra-ordinary post-treatment of the fibers. It is a further object of this invention to provide a polyolefin fiber having durable wettability.